Hydraulically operated apparatus



July 14. 1964 KARL-EVERT A. JOELSON 3,140,536

HYDRAULICALLY OPERATED APPARATUS 2 Sheets-Sheet 1 Filed Sept. 11, 1961 FIG.|

5 9 .n r //%#K 7 r 6 7 a 1 4 TTORNE July 14, 1964 KARLEVERT JOELSON HYDRAULICALLY OPERATED APPARATUS 2 Sheets-Sheet 2 Filed Sept. 11, 1961 INVENT OR KARL- E VERT' ANDE'RS JOE'LSON United States Patent 3,140,586 HYDRAULICALLY OPERATED APPARATUS Karl-Evert Anders Joelson, Torget 2, Nykoping, Sweden Filed Sept. 11, 1961, Ser. No. 137,372 Claims priority, application Sweden Sept. 19, 1960 V 6 Claims. (Cl. 60-545) The present invention relates to a hydraulically operated apparatus, particularly percussive apparatus comprising a reciprocatory drive member and an impact member driven by the drive member.

If the drive member and impact member are mechanically connected, the length of the impact stroke of the impact member is limited by the turning point of the drive member at the end of the working stroke. To prevent this, the drive member may be disconnected from the impact member during the working strokes of the members. Furthermore the force of the impact is dependent upon the kinetic energy of the impact member. Since the drive member reciprocates, its speed reaches a maximum'between the ends of its working or drive stroke. In order to achieve the maximum impact force, it is necessary for the impact to occur when the speed of the impact member is a maximum. When the drive and impact members are mechancially connected it is very hard to locate the apparatus and workpiece so that the impact occurs when the speeds of the members are a maximum. Thus, in order to achieve maximum impact force and length of impact stroke, it is necessary for the impact member to be freely movable independently of the drive member after the latter has reached its maximum speed during its working stroke. This, as mentioned above, entails disconnecting the drive member and impact member during the working strokes and reconnecting them by the commencement of the next working stroke.

In an apparatus according to this invention a hydraulically operated percussive apparatus comprises a reciprocatory drive member, a reciprocatory impact member, a hydraulic drive connection between said members such that movement of said drive member hydraulically drives said impact member, and valve means operable, by movement of one of said members into a certain position, to disconnect said hydraulic drive connection.

By selecting the ratio between the diameters of the drive and impact pistons, it is possible to obtain a high impact piston speed with a low drive piston speed.

The drive and impact members are preferably pistons slidable in first and second cylinders respectively; in this case the cylinders are interconnected by passageway means and form with the latter a closed chamber. The cylinders and passageway means may be formed coaxially in the same metal block with the passageway means forming an extension of the second cylinder, or the cylinders may be separate and connected by passageway means in the form of pipe. The hydraulic drive connection is preferably disconnected by valve means operative, when the drive piston reaches a certain position, in its working stroke, to interconnect a liquid reservoir and the closed chamber.

The invention is described in greater detail with refence to the accompanying drawings in which:

FIG. 1 is a view partially in axial cross section and partially in elevation of a first illustrative embodiment of a percussive apparatus or tool according to the invention; and

FIG. 2 is a view partially in axial cross section and partially in elevation of a second illustrative embodiment of percussive apparatus or tool according to the invention.

The impact or percussive apparatus comprises an outer closed casing or housing 1 which forms a liquid reservoir and which, in use, is substantially filled with pressure liquid. A first cylinder 6, which is similarly fitted with liquid, is mounted in the housing. A drive piston 4 is located in the first cylinder and may, for example, be driven by a rotating drive element such as a cam or eccentric 2 or other suitable device. The eccentric 2 may be connected to a flywheel 3. An operating piston or impact or percussive piston 8 is mounted in a second cylinder and a sealing ring 10 prevents leakage past it. The first and second pistons are interconnected by passageway means which in the illustrated embodiment form an extension of the second cylinder. In the illustrated embodiment the pistons may be returned-that is moved on their return or inward strokesto their initial positions by means such as springs 7 and 11. Instead of the return spring 11 hydraulic pressure from an external pressure source may be used or a secondary piston may be incorporated in the machine.

The first and second cylinders form with their passageway means a closed chamber which can communicate with the outer housing or casing 1 through valve means including a check valve 5 and an outlet 9. The operating or impact piston 8 has a smaller diameter than the drive piston 4, and in consequence hereof, the second cylinder has a smaller diameter in the range of movement of the impact piston 8 than in the range of movement of the drive piston 4.

The arrangement functions in the following manner. When the eccentric 2 is rotated the drive piston 4 is forced downwardly with, for example, the normal speed of piston pumps e.g. 1-2.5 metres/second. At the same time the check valve 5 is closed by the pressure produced in the cylinder 6 as a result ofthe movement of the drive piston; this pressure also forces the operating or impact piston 8 downwardly. On account of the smaller diameter of the second cylinder, the latter piston moves at a higher speed, for example 8 metres/second, than the drive piston 4. Both pistons achieve approximately the maximum speed when the eccentric has turned through At this instant the operating or impact piston 8 strikes the tool or the workpiece (not shown) while the eccentric continues to force the drive piston 4 downwardly at a decreasing speed. When the operating piston 8 has achieved its maximum speed and struck the workpiece the valve means formed by the piston 8 and outlets 9 place the closed chamber including the cylinder 6 in communication with the housing 1. Consequently the impact piston is no longer forced forwardly; instead the drive piston 4 forces liquid into the outer housing 1. On the return of the drive piston the check valve 5 is opened and liquid enters the closed space 6.

Since the greater part of the power is given off by the drive piston during 90 rotation of the eccentric from the zero position, it is advantageous to connect the eccentric with the above-mentioned flywheel 3 as in this manner to store the surplus energy. During the rotation of the eccentric from to 360 both pistons are returned by their respective springs or other devices.

If the apparatus is driven by a hydraulic motor, it may be advantageous to cause a small proportion of the liquid stream from the hydraulic motor to flow through the housing 1, partly, so as to fill it and, partly, to remove heated liquid from the apparatus (the tool). When the apparatus or tool is hydraulically driven by an electric motor or the like or by a pump hydraulic motor, a cooling coil for the motor may be arranged to cool the tool as well in the manner stated above.

In comparison with mechanical power transference, hydraulic power transference according to the invention offers many advantages. Mechanical power transference involves special difficulties owing to the fact that a crank or eccentric movement has only a small straight line movement at or adjacent the turning positions, and as ais sse a result some type of disconnection clutch device must be used so as to utilise the impact or percussive force at the maximum speed of the crank arm or eccentric. This difficulty is avoided according to the invention by placing the cylinder 6 in communication with the outer casing 1 when the pistons have attained maximum speed, whereby the operating piston is disconnected or becomes independent of the continued movement of the drive piston. This clutch disconnection position may be selected as desired and may also be adjusted, for example by using the above described grooves or passages 9, 12, 13.

Further advantages of the arrangement according to the invention is the storage of power during more than 180 of eccentric rotation by the flywheel, and the higher speed of the operating or impact piston in comparison with the drive piston owing to the different diameters of the cylinder in the ranges of the respective pistons. The hydraulic drive is furthermore accompanied by an appreciable power saving, for example in comparison with pneumatic tools which may use 2.5 times as much energy to obtain the same output.

In FIG. 2 there is shown a second illustrative embodiment of percussive apparatus which is the same as that of FIG. 1 except for the character of the means providing communication between the first and second cylinders thereof. Accordingly, parts in FIG. 2 which are generally the same as those in FIG. 1 are designated by the same reference characters with an added prime.

In FIG. 2 there are substituted for the outlets 9 other means which function in generally the same manner but permit adjustment of the time at which the second, lower cylinder is placed in communication with the housing 1. Thus, in FIG. 2 the piston 4 is provided at its upper end with a spiral groove 12. The sidewalls of the lower cylinder are imperforate, and the inner sidewall of cylinder 6 is provided with a vertically extending groove 13 which terminates at its upper end at a shoulder 14. It will be understood that in the position of the parts shown in FIG. 2 the groove 12 is out of communication with groove 13, lying above shoulder 14 of the latter groove. The space within the upper and lower cylinders will be filled with liquid through check valve 5.

As cam 2 rotates from the position thereof shown in FIG. 2, the check valve 5' is closed, and the piston 4 is forced downwardly. The pressure in cylinder 6 as a result of the downward travel of piston 4 forces the impact piston 8 downwardly until piston 4 has moved sufficiently to bring groove 12 thereon into communication with groove 13. Thereupon the fluid above piston 8 is exhausted to the housing through grooves 13 and 12, so that piston 8 is no longer subjected to hydraulic pressure which drives it downwardly. On the return stroke of the drive piston, the check valve 5' is opened, and liquid enters the space within cylinder 6.

The arrangement of FIG. 2 permits adjustment of the time of cut-off of the driving downwardly of piston 8 by rotating the piston 4' relative to the cylinder 6'. This permits the position at which grooves 12 and 13 are placed in communication to be varied appreciably, thereby affording an adjustment of the length of stroke of the impact piston 8.

What I claim is:

1. A hydraulically operated percussive apparatus comprising a sump on the apparatus, containing hydraulic liquid, a first cylinder, a drive piston slidable in said first cylinder, eccentric means for reciprocating said drive piston so that the drive piston attains its maximum speed in the driving direction at a position intermediate the ends of its stroke, a second cylinder having a smaller diameter than said first cylinder, an impact piston slidable in said second cylinder, passageway means between the first and second cylinders, means to supply the passageway means with liquid from the sump, whereby movement of said drive piston in its driving direction hydraulically drives said impact piston, and valve means for bleeding hydraulic liquid from the passageway means to the sump, and thus disconnecting the hydraulic drive between said pistons, on each pressure stroke of the drive piston at said intermediate position at which it attains its maximum speed.

2. A hydraulically operated apparatus comprising a liquid reservoir; a block having formed therein a first cylinder, a second cylinder having a smaller diameter than said first cylinder and a conduit interconnecting said first and second cylinders to form with said cylinders a closed chamber; a drive piston slidable in said first cylinder; cam means for moving said drive piston inwardly in said first cylinder on its working stroke; means for moving said drive piston outwardly in said cylinder on its return stroke; an impact piston slidable in said second cylinder, said drive piston on its Working stroke being operative to displace liquid from said first cylinder into said second cylinder to drive said impact piston on the working stroke of the latter; means to move said impact piston inwardly in said second cylinder on its return stroke, and valve means operative to disconnect the hydraulic drive connection between said first and second cylinders, said valve means comprising a passage which is uncovered by one of said pistons during its working stroke to interconnect said chamber and reservoir, and a check valve located between said chamber and reservoir and operative to permit liquid to flow from said reservoir into said chamber.

3. A hydraulically operated impact apparatus comprising a liquid reservoir; a first cylinder; a second cylinder coaxial with said first cylinder and having a smaller diameter than said first cylinder; a conduit interconnecting said first and second cylinders to form with said cylinders a closed chamber; a drive piston slidable in said first cylinder; an eccentric adapted to be driven by a motor and to move said drive piston inwardly in said first cylinder on its working stroke; a spring housed in said first cylinder for moving said drive piston outwardly in said cylinder on its return stroke; a flywheel connected to said eccentric; an impact piston slidable in said second cylinder, said drive piston on its working stroke being operative to displace liquid from said first cylinder into said second cylinder to drive said impact piston on its working stroke; a spring for moving said impact piston inwardly in said second cylinder on its return stroke; and valve means operative to disconnect the hydraulic drive connection between said first and second cylinders upon said eccentric having rotated from the position in which said drive piston commenced its working stroke, said valve means comprising a passage which is uncovered by said impact piston during its working stroke to interconnect said chamber and reservoir, a check valve mounted in said drive piston between said chamber and reservoir and operative to permit liquid flow from said reservoir into said chamber, and a pair of cooperating grooves formed in the walls of said first cylinder and drive piston respectively and adapted to register to interconnect said chamber and reservoir.

4. A hydraulically operated apparatus comprising a first cylinder, a drive piston reciprocable in said first cylinder, means for reciprocating said drive piston, a second cylinder, an operating piston reciprocable in said second cylinder, passageway means hydraulically interconnecting said first and second cylinders to form with said cylinders a closed chamber such that said drive piston during its working stroke displaces liquid into said second cylinder to drive said operating piston outwardly in said second cylinder on its working stroke, a liquid reservoir, valve means including said operating piston adapted to open to put said chamber in communication with said reservoir during the latter part of the working stroke and the first part of the return stroke of said drive piston to disconnect the hydraulic drive connection between said drive and operating pistons. said valve means comprising a groove in the wall of said first cylinder and a groove in said drive piston, said grooves registering with each other during the latter part of the working stroke and first part of the return stroke of said drive piston to establish said communication, and return means for moving said operating piston inwardly in second cylinder on its return stroke.

5. A hydraulically operated percussive apparatus comprising a first hydraulic cylinder, a drive piston slidable in said cylinder, a second hydraulic cylinder in communication with said first cylinder, an impact piston slidable in said second cylinder, at source of hydraulic liquid, means for supplying hydraulic liquid from said source to said cylinders so as to serve as a hydraulic drive connection between said pistons, means for reciprocating said drive piston, valve means for disconnecting the hydraulic drive between said pistons when said drive piston has attained its maximum speed at each working stroke, said valve means comprising a passage communicating with the interior of said cylinders and with said source of hydraulic liquid, a valve body in said passage for opening the passage when said drive piston has attained a predetermined position corresponding to its maximum speed and a check valve operative to permit hydraulic liquid from said source to flow from said source into said cylinders during the return stroke of said drive piston.

6. A hydraulically operated percussive apparatus comprising a first cylinder, a drive piston reciprocally slidable in said first cylinder, a second cylinder having a smaller diameter than said first cylinder, an operating piston reciprocally slidable in said second cylinder, passageway means hydraulically connecting said first cylinder to said second cylinder to form with said drive piston and said operating piston a closed chamber such that said drive piston during its working stroke displaces liquid into said second cylinder to drive said operating piston outwardly in said second cylinder on its working stroke, rotatable means for sliding said drive piston in said first cylinder, said rotatable means shaped to cause said drive piston during said working stroke to start from an initial position and continuously increase its speed until a maximum speed is attained and then to continuously decrease its speed until a turning position is reached, said maximum speed occurring between said initial position and said turning position, a liquid reservoir, valve means comprising a passage Which is uncovered by one of said pistons to put said closed chamber formed between said drive piston and said operating piston in communication with said liquid reservoir upon said drive piston attaining said maximum speed during each working stroke and to maintain said communication during the remainder of each Working stroke and during a substantial portion of each return stroke of said drive piston, said valve means closing during each said return stroke and remaining closed until said drive piston attains said maximum speed during said working stroke, and return means for moving said operating piston inwardly in said second cylinder during said operating pistons return stroke.

References Cited in the file of this patent UNITED STATES PATENTS 2,638,749 Sparano May 19, 1953 2,645,138 Mitchhart July 14, 1953 2,882,685 Carlsen et al. Apr. 21, 1959 2,919,650 Wiggermann Jan. 5, 1960 2,982,255 Klenck May 2, 1961 FOREIGN PATENTS $7 2,844 France Mar. 2, 1907 

1. A HYDRAULICALLY OPERATED PERCUSSIVE APPARATUS COMPRISING A SUMP ON THE APPARATUS, CONTAINING HYDRAULIC LIQUID, A FIRST CYLINDER, A DRIVE PISTON SLIDABLE IN SAID FIRST CYLINDER, ECCENTRIC MEANS FOR RECIPROCATING SAID DRIVE PISTON SO THAT THE DRIVE PISTON ATTAINS ITS MAXIMUM SPEED IN THE DRIVING DIRECTION AT A POSITION INTERMEDIATE THE ENDS OF ITS STROKE, A SECOND CYLINDER HAVING A SMALLER DIAMETER THAN SAID FIRST CYLINDER, AN IMPACT PISTON SLIDABLE IN SAID SECOND CYLINDER, PASSAGEWAY MEANS BETWEEN THE FIRST AND SECOND CYLINDERS, MEANS TO SUPPLY THE PASSAGEWAY 